若圆x2+y2-ax+2y+1=0与圆x2+y2=1关于直线y=x-1对称,过点C(-a,a)的圆P与y轴相切,则圆心P的轨迹方程为( )。
y2+4x-4y+8=0
低钾性碱中毒常出现于
A.尿毒症B.胃肠减压C.术后少尿D.挤压创伤E.输血过量
We know Jackie Chan _____ movies are very popular with the young. [ ]
A. whose
B. that
C. who
D. which